Urinary tract infections should be considered in any infant 2 months to 2 years who presents with a fever without localization. The earlier the diagnosis, the less risk of renal scarring and the earlier detection of anatomical abnormalities. In older children, symptoms will lead to evaluation for an infection.

Pathogenesis

Escherischia coli. by far the most common organism causing UTIs and accounts for 85 percent of all UTIs in children. Other organism to consider are Klebsiella pneumoniae, Proteus vulgaris, Enterobacter, Staphylocoocus saprophyticus, Citrobacter, Enterococcus and Pseudomonas aeruginosa. Gram positive organism are uncommon pathogens of UTIs in children

Usually are secondary to ascending infection.

Once the bladder is contaminated the risk of infection is related to the emptying of the bladder and voiding habits. Incomplete or infrequent emptying will lead to bacterial overgrowth.

Pyelonephritis- indirect evidence of renal infection with fever, increased ESR and CRP, increased WBCs on CBC, decreased concentrating ability of the kidney, and CVA tenderness. These changes are not specific and sensitive when DMSA scan is done to verify kidney involvement

History

Positive family history of reflux

Incomplete voiding, dribbling, daytime wetting

Weak urinary stream

Physical Examination

Growth record

Blood pressure

Abdominal exam- palpating for mass. Check for CVA tenderness.

Examination of external genitalia for signs of irritation, trauma, and other abnormalities

Suprapubic or costovertebral tenderness is a sign of a UTI, but other findings are nonspecific.

Observation of urinary stream

Rectal exam to rule out impaction

Laboratory Findings

Nitrite test- Best in overnight urine to allow time for bacteria to convert nitrate to nitrite in the bladder. Gram positive organisms will not give a positive nitrite test. About 50% sensitivity and 98% specific

WBCs- are markers for inflammation. Bacteriuria without WBCs of questionable significance and may obviate need for urine culture.

Culture- should be fresh (<30 minutes and kept cold)

A bagged urine is only significant if culture is negative

Midstream urine is useful in older females and males

Catheterized and suprapubic specimens are most reliable for culture.

Interpretation

Suprapubic specimen

any gram negative organism is positive.

> 1,000 CFU per mL is positice

Catheterized specimen

> 10,000 organisms infection likely

Clean Void

Boy- > 100,000 infection likely

Girl 3 specimens of > 100,000 infection likely 95%

2 specimens of > 100,000 infection likely 90%

1 specimen of > 100,000 infection likely 80%

10,000-100,000 and clinical suspicion suggest repeating culture

< 10,000 infection unlikely

Management of Positive Culture

If symptoms are mild, treat with PO Bactrim, Augmentin or 2nd or 3rd generation Cephalosporin

Followup assessment should be done at 48 to 72 hours to confirm adequate clinical response.

If symptoms are severe, use parenteral antibiotics to cover gram positive and gram negatives. Can use 2nd or 3rd generation Cephalosporin and Gentamycin. Must adjust treatment after obtaining results of the culture and sensitivity.

Treat for 10-14 days---However, a review in American Family Physician notes that a two to four day course of oral antibiotics is just as effective for lower UTIs

Repeat culture if symptoms are persisting after two days of therapy, sensitivities not done prior to treatment, and at the end of treatment.

Child should be on prophylaxis awaiting imaging studies. Acceptable drugs include Bactrim, Nitrofurantoin, Sulfisoxazole, Nalidixic Acid. Prophylaxis is controversial, however, and may not reduce risk of recurrent UTIs in patients with mild reflux.

Treatment of young infants with fever and UTI- a recent study has demonstrated that oral treatment with Cefixime is as effective as intravenous treatment with Cefotaxime and there was no increase of renal, scarring, length of fever, time to sterilize the urine, and reinfections.

Acute pyelonephritis can be treated with oral antibiotics, such as cefixime, amoxicillin/clavulanate, ceftibuten for 14 days or a two to four day course of IV therapy followed by oral therapy.

Imaging Studies

Imaging studies are necessary to demonstrate the urinary tract anatomy and functional status. There are differing opinions on who and when they should be performed.

Ultrasound and voiding cystourethrogram (VCU) should be done after the first UTI for all boys, girls younger than three and girls three to seven years old with a temperature of 101.3 or more. If a followup VUG is needed, usually do nuclear cystogram to decrease radiation exposure.

Alternative is ultrasound and renal cortical scan

The presence of a normal fetal ultrasound may obviate the need for further imaging studies. This is presently under study.

Follow-up

May follow urines at home with nitrite reagent sticks

Refer to pediatric urologist if there are recurrent infections associated with anatomic defects or obstruction.

Roberts KB. A Synopsis of the American Academy of Pediatrics' Practice Parameters on the Diagnosis, Treatment and Evaluation of the Initial Urinary Tract Infection in Febrile Infants and Young Children. Pediatrics in Review. 1999; 20:344-347...